Preparation of black sand-based magnetic photocatalysts for photocatalytic oxidation of aqueous phenol

A natural magnetic material, black sand, was used as cores to prepare a magnetic photocatalyst, which can be recovered using an external magnetic field. A surfactant-involved scheme was proposed to deposit a rough silica layer on the surface of black sand, which otherwise could not be coated with silica through a conventional scheme involving Stöber process. Titanium dioxide (TiO2) was deposited on the surface of the silica–black sand (Si/BS) through an impregnation process and a direct deposition process. The catalytic property of the resultant photocatalyst (Ti/Si/BS) was evaluated using the oxidation of aqueous phenol and exhibited less reactivity than Degussa P25 TiO2. The phenol removal efficiency showed a pH dependence, which was ascribed to pH effect on (a) the formation of *OH and (b) the electrostatic interaction between the photocatalyst and the substrate. The prepared photocatalyst is reusable despite slight deactivation caused by the mechanical loss of TiO2.